1. Field of the Invention
The present invention relates to a new metal complex dye used mainly for leather dyeing, a method of its production and a metal-tanned leather dyeing method using said metal complex dye. 2. Description of the Prior Art
The majority of dyes used for leather dyeing are anionic dyes having a water-soluble group, such as acid dyes, direct dyes, metal complex dyes and mordant dyes. For dyeing chromium-tanned leather and other highly cationic leather, dyes having a sulfo group have conventionally been used in almost all cases.
For example, Japanese Patent Publication Open to Public Inspection Nos. 40357/1983, 59871/1981, 171776/1982, 171778/1982 and 259685/1985 propose metal complex dyes with the aim of improving various properties including color fastness to rubbing, color fastness to water, color fastness to washing, color fastness to light, dyeing property, leveling property and permeability. These dyes all have a sulfo group or a carboxyl group as a water-soluble group.
However, the dyes and dyeing methods which have conventionally been used to dye leather, particularly metal-tanned leather, are not fully satisfactory with respect to dyeing power, color fastness to rubbing and permeability.
The present invention was developed in consideration of these aspects. The object of the invention is to provide a metal complex dye that offers good permeability and excellent color fastness to rubbing and color fastness to light particularly in metal-tanned leather dyeing, a method of its production and a metal-tanned leather dyeing method.